The technique of measuring neutron multilayer monochromator reflectivities by double diffraction rocking curves is discussed. Two problems encountered are deposition induced curvature of multilayer support and lateral variation of layer spacing. Transmitted rocking curves were measured with a narrow detector in an effort to understand these specific problems. General formulae for interpretation of such rocking curves are derived and the methodology for determining relevant parameters is discussed. Measured reflectivities of 10 nm spacing Ni-Ti multilayer devices are presented. Consideration of support curvature and layer spacing variation is essential in understanding observed data.